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PhoTheNguyen85 5.3K Views
Apr 28, 2026 4:36 PM

YMMV: Castrol GTX High Mileage Synthetic Blend 5 Quart in various grade $14.95

$15

$30

50% off
Advance Auto Parts
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Local Advance Auto Parts have various grade Castrol GTX High Mileage Synthetic Blend on clearance for $14.95. On top of that, there is a rebate for $5 back via PayPal or Venmo essentially making a 5 quart $10. Limit 3 rebate.

https://www.castrol.com/en_us/uni...tions.html

https://shop.advanceautoparts.com...hicle=true
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About the Poster
Local Advance Auto Parts have various grade Castrol GTX High Mileage Synthetic Blend on clearance for $14.95. On top of that, there is a rebate for $5 back via PayPal or Venmo essentially making a 5 quart $10. Limit 3 rebate.

https://www.castrol.com/en_us/uni...tions.html

https://shop.advanceautoparts.com...hicle=true

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Apr 28, 2026 8:42 PM
225 Comments
Joined Mar 2015
fandrew7Apr 28, 2026 8:42 PM
225 Comments
This is a good deal, but various weights are available on Amazon for this same price. For the five dollar rebate savings I'd rather not have to deal with advanced autos incredibly inaccurate inventory and the gas to go get it.
Apr 28, 2026 8:55 PM
4K Comments
Joined Oct 2010
brotherhpj41Apr 28, 2026 8:55 PM
4K Comments
Always wondered:
Synthetic blend motor oil generally contains between 10% and 25% synthetic base oil mixed with conventional oil, though some blends may vary from as little as 1% to as high as 60%. There is no industry-wide standard defining the exact percentage required, allowing manufacturers to decide the ratio, often keeping it closer to the lower end for cost reasons
Apr 28, 2026 11:33 PM
225 Comments
Joined Mar 2015
fandrew7Apr 28, 2026 11:33 PM
225 Comments

Our community has rated this post as helpful. If you agree, why not thank

Quote from brotherhpj41 View quoted comment :
Always wondered:
Synthetic blend motor oil generally contains between 10% and 25% synthetic base oil mixed with conventional oil, though some blends may vary from as little as 1% to as high as 60%. There is no industry-wide standard defining the exact percentage required, allowing manufacturers to decide the ratio, often keeping it closer to the lower end for cost reasons
While full synthetic is a better option on any engine that doesn't have leaky seals, semi synthetic will often leak less than full synthetic if you have old or dry seals. Conventional will leak even less. It's not uncommon for an older engine like Jeep's 4.0 to visibly drip full synthetic but be completely dry with conventional oils. Every engine is different and the type of oil (which detergent packs are used in the blend) matters. If you have a small leak/drip try switching to something like white bottle Castrol (conventional) or a semi-synthetic like gtx high mileage if you need the thinner viscosity.
Source: mechanic for ~25 years
4
Apr 30, 2026 1:56 AM
1.4K Comments
Joined Dec 2008
ZV3Apr 30, 2026 1:56 AM
1.4K Comments
Not sure who a semi-synthetic is marketed to, somebody who ALMOST wants the best? Someone who wants to save a few bucks over full synthetic but not reap any benefits? Just go full synthetic for 3 or 4 bucks more.
Apr 30, 2026 4:41 PM
274 Comments
Joined Nov 2022
WthaHatchetApr 30, 2026 4:41 PM
274 Comments
Quote from fandrew7 View quoted comment :
This is a good deal, but various weights are available on Amazon for this same price. For the five dollar rebate savings I'd rather not have to deal with advanced autos incredibly inaccurate inventory and the gas to go get it.
If you order from them, Advance auto, make sure you check your email for either order ready for pickup or canceled before going. Will stop you from going for nothing. Just fyi. They aren't always inaccurate. Depends on the individual stores.
Apr 30, 2026 4:44 PM
274 Comments
Joined Nov 2022
WthaHatchetApr 30, 2026 4:44 PM
274 Comments
Quote from fandrew7 View quoted comment :
While full synthetic is a better option on any engine that doesn't have leaky seals, semi synthetic will often leak less than full synthetic if you have old or dry seals. Conventional will leak even less. It's not uncommon for an older engine like Jeep's 4.0 to visibly drip full synthetic but be completely dry with conventional oils. Every engine is different and the type of oil (which detergent packs are used in the blend) matters. If you have a small leak/drip try switching to something like white bottle Castrol (conventional) or a semi-synthetic like gtx high mileage if you need the thinner viscosity. Source: mechanic for ~25 years
If you have and older engine the high mileage synthetic has additives that make the seals swell more. So leaking can be the same depending on if you used the high mileage or not. Id do agree though regular motor oil is thicker for some reason even at the same weight it seems.
May 1, 2026 2:52 AM
2.8K Comments
Joined Oct 2008
asukaMay 1, 2026 2:52 AM
2.8K Comments
As usual, old engine? Great.

Turbo? Supercharger? Timing chain? Get an API SQ full synthetic.
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May 1, 2026 6:17 AM
1.1K Comments
Joined Apr 2014
mouthforwarMay 1, 2026 6:17 AM
1.1K Comments
Amazon has 10W-30 and 5W-20 for the same price (cheaper with S&S) if those suits your needs: https://www.amazon.com/Castrol-03...43WE/?th=1

https://www.amazon.com/Castrol-03...LS64/?th=1
Last edited by mouthforwar April 30, 2026 at 11:19 PM.
May 3, 2026 1:48 PM
14 Comments
Joined Jul 2017
dkelsey56436May 3, 2026 1:48 PM
14 Comments
Quote from fandrew7 View quoted comment :
While full synthetic is a better option on any engine that doesn't have leaky seals, semi synthetic will often leak less than full synthetic if you have old or dry seals. Conventional will leak even less. It's not uncommon for an older engine like Jeep's 4.0 to visibly drip full synthetic but be completely dry with conventional oils. Every engine is different and the type of oil (which detergent packs are used in the blend) matters. If you have a small leak/drip try switching to something like white bottle Castrol (conventional) or a semi-synthetic like gtx high mileage if you need the thinner viscosity. Source: mechanic for ~25 years
My Northstar just said "hold my cosmo"
May 21, 2026 5:34 PM
6.7K Comments
Joined Mar 2011
ballershanelleMay 21, 2026 5:34 PM
6.7K Comments
Submitted 3 jugs on 5/13. It paid out on 5/21/26..two separate submissions. Easy moolah. Basically, $10 a piece w speed perks growing ...
Last edited by ballershanelle May 21, 2026 at 10:45 AM.

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